1. Field
The present invention relates to a brake system for a motorcycle.
2. Description of the Related Art
By-wire type brake devices (BBW: brake-by-wire) have been put to practical use. In this type of brake device, an amount of operation on the brake (brake operation amount) is detected, then a hydraulic pressure is generated in a hydraulic modulator on the basis of the detected value, and a braking force is generated by the hydraulic pressure.
By the above-mentioned brake device (BBW), an ABS (antilock brake system) function can be exhibited.
Furthermore, there has been known a system in which not only the ABS function is exhibited by the brake device as above-mentioned but also front and rear brake devices are operated in an interlocked manner by operating one of front and rear brake operating members (see, for example, FIGS. 1 and 3 of Patent Document 1 (Japanese Patent Laid-Open No. 2006-175993)).
The system in which front-wheel and rear-wheel brake devices are operated in an interlocked manner is called a CBS (combined brake system). When a mode change-over switch 32 shown in FIG. 1 of Patent Document 1 is switched over, a CBS function is selected, whereby a front wheel braking force and a rear wheel braking force are controlled based on a predetermined correlation, as shown in FIG. 3 of Patent Document 1.
In this way, in the CBS function according to the related art, the front-rear distribution of braking force is unequivocally determined. From the driver's point of view, however, there is a demand for changing the front-rear distribution correspondingly to variations in the running environments such as changes between traveling on a public road and traveling on a circuit racecourse, or variations in road conditions such as changes between a dry road surface and a wet road surface. For instance, a desirable front-rear distribution at the time of straight forward traveling or that at the time of putting priority on vehicle body control during turning, in the case where the coefficient of friction (μ) on a road is high and a high braking force at the tire can be expected, are different from the front-rear distributions favored in the case where the coefficient of friction on a road is low. Thus, there is a demand for changing the front-rear distribution of braking force according to the running environments. Accordingly, there is room for further improvement in order to make it possible to cope with variations in the front-rear distribution of braking force according to various parameters or environmental conditions.